吴彦旺, 李才, 徐梦婧, 解超明, 王明, 熊盛青, 范正国. 藏北羌塘中部果干加年山石炭纪蛇绿岩地球化学特征及LA-ICP-MS锆石U-Pb年龄[J]. 地质通报, 2014, 33(11): 1682-1689.
    引用本文: 吴彦旺, 李才, 徐梦婧, 解超明, 王明, 熊盛青, 范正国. 藏北羌塘中部果干加年山石炭纪蛇绿岩地球化学特征及LA-ICP-MS锆石U-Pb年龄[J]. 地质通报, 2014, 33(11): 1682-1689.
    WU Yan-wang, LI Cai, XU Meng-jing, XIE Chao-ming, WANG Ming, XIONG Sheng-qing, FAN Zheng-guo. Geochemical characteristics and LA-ICP-MS zircon U-Pb geochronology of Guogangjianan Carboniferous ophiolite in central Qiangtang, the Tibetan Plateau[J]. Geological Bulletin of China, 2014, 33(11): 1682-1689.
    Citation: WU Yan-wang, LI Cai, XU Meng-jing, XIE Chao-ming, WANG Ming, XIONG Sheng-qing, FAN Zheng-guo. Geochemical characteristics and LA-ICP-MS zircon U-Pb geochronology of Guogangjianan Carboniferous ophiolite in central Qiangtang, the Tibetan Plateau[J]. Geological Bulletin of China, 2014, 33(11): 1682-1689.

    藏北羌塘中部果干加年山石炭纪蛇绿岩地球化学特征及LA-ICP-MS锆石U-Pb年龄

    Geochemical characteristics and LA-ICP-MS zircon U-Pb geochronology of Guogangjianan Carboniferous ophiolite in central Qiangtang, the Tibetan Plateau

    • 摘要: 在羌塘地区开展1∶5万戈木日区域地质调查的过程中,为研究龙木错—双湖板块缝合带的演化历史,探讨青藏高原羌塘中部地区的构造演化,对果干加年山地区的蛇绿岩进行了详细研究。石炭纪蛇绿岩变质堆晶辉长岩是填图过程中的新发现。全岩地球化学研究结果显示,岩石ΣREE较低,LREE弱富集,轻、重稀土元素分异程度不高;富集Rb、Bb等大离子亲石元素,明显亏损Nb、Ta、Ti等元素,具有典型的SSZ型蛇绿岩特征,表明其形成于俯冲带之上。蛇绿岩中变质堆晶辉长岩的LA-ICP-MS锆石U-Pb年龄为354.8Ma±2.4Ma,属于早石炭世。最终研究表明,龙木错—双湖板块缝合带所代表的古大洋至少在早石炭世就已经存在俯冲。石炭纪变质堆晶辉长岩的发现对研究缝合带构造演化历史具有非常重要的意义,也为探讨羌塘地区的大地构造演化提供了基础资料。

       

      Abstract: In order to investigate the evolution of the Lungmu Co-Shuanghu plate suture zone and the tectonic history of central Qiangtang, the authors studied Guoganjianian ophiolite in the aspects of petrology, geochemistry and geochronology. The cumulate in Guoganjianian ophiolite was recently discovered during 1∶50000 regional geological survey of the Gemuri area. Geochemical studies show that the cumulate gabbro has low REE content and flatten REE patterns with slight enrichment of LREE, and the degree of differentiation between LREE and HREE is low. These samples are enriched in large ion lithophile elements (LILE) such as Rb and Ba, and depleted in Nb, Ta and Ti, suggesting that they were probably formed in a subduction zone. LA-ICP-MS technique was applied to U-Pb zircon dating of the cumulate gabbro from Guoganjianian ophiolite. The result shows that the ages of cumulate gabbro is 354.8Ma±2.4Ma, suggesting that Lungmu Co-Shuanghu Ocean already began its subduction in Early Carboniferous. The study of Guoganjianian cumulate gabbro provides important basic data for investigating the evolution of Lungmu Co-Shuanghu plate suture zone and the tectonic history of central Qiangtang.

       

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